Extremely irritated and upset

Since Nov 2020 MTN has been suspending my line 2 or 3 times a month with the complaint that I missed a payment in August 2020. I emailed *** my proof of payments and on 29 December 2020, they sent me a confirmation that all was sorted BUT NO! At some point, MTN, who I've been with since 1996, must sort out their accounts department. I'm sick and tired to have my line cut simply because they are ***********.